Deep VLT spectroscopy of the z=2.49 radio galaxy MRC 2104-242 - Evidence for a metallicity gradient in its extended emission line region

We present spectroscopic observations of the rest-frame UV line emission ar ound radio galaxy MRC 2103-242 at z = 2.49, obtained with FORS1 on VLT Antu . The morphology of tile halo is dominated by two spatially resolved region s. Ly alpha is extended by > 12 " along tile radio axis, C IV and He II are extended by similar to8 ". The overall spectrum is typical for that of hig h redshift radio galaxies. The most striking spatial variation is that N V is present in tile spectrum of the region associated with the center of the galaxy hosting: the radio source, the northern region, while absent in the southern region. Assuming that the gas is photoionized l,a a hidden quasar , the difference in N V emission can be explained by a metallicity gradient within the halo, with the northern region having: a metallicity of Z appro ximate to 1.5 Z(circle dot) and Z less than or equal to 0.4 Z(circle dot) f or the southern region. This is consistent with a scenario in which tile ga s is associated with a massive cooling: Bow or originates from the debris o f tile merging of two or more galaxies.